Alexander Mackay Mackenzie

Weaning is a time of acute stress for the piglet, as it transitions from dependence on the sow and her milk to social and nutritional independence (Weary et al. 2008). This coincides with a change ...

Excessive copper (Cu) absorption in calves may increase the risk of excessive hepatic Cu accumulation, likely driven by their elevated pre-ruminant absorptive capacity, with the potential for harmful Cu accumulation leading to adverse health and productivity outcomes. However, quantitative data across the weaning transition remains limited. This study utilized secondary data and bio-banked samples from 35 Holstein–Friesian bull calves to estimate hepatic Cu retention coefficients pre- and post-weaning. Although mean hepatic Cu concentrations remained broadly stable throughout the study, between 311 and 675 mg/kg of DM, changes varied by developmental stage: calves experienced hepatic Cu accumulation of 2.5 mg of Cu/kg of DM/d pre-weaning but a net reduction of 1.8 mg/kg of DM/d post-weaning. Pre-weaning calves exhibited a hepatic Cu retention coefficient of 81% compared to post-weaning calves, where the hepatic Cu retention coefficient was 5%. This reduction in absorptive capacity is consistent with increased rumen development and greater antagonism from dietary sulfur and molybdenum. Hepatic steady-state Cu intake requirements were estimated at 3 mg/kg of DM pre-weaning and 15 mg/kg of DM post-weaning. These findings demonstrate that the pre-weaning period represents a phase of high Cu retention and heightened susceptibility to hepatic Cu accumulation, even when dietary Cu meets current recommendations. Refining Cu feeding guidelines to more accurately reflect developmental stage and rumen maturation may help prevent excessive hepatic Cu loading while maintaining adequate mineral supply.

Policies implemented by milk buyers and the Great Britain (GB) calf strategy aim to prevent the on-farm euthanasia of healthy dairy-bred calves and align the management with that of replacement heifers. The welfare of dairy-bred calves is influenced by multiple factors, many of which are driven by management decisions that reflect the values and perceptions of farm managers and calf rearers. Workload is maximized in block calving systems wherein calves are born within a 12-week period, thus potentially exaggerating differing views on calf value. This paper explores the perceived value of dairy heifer and surplus calves in English block calving systems and investigates how this and other factors affect calf management. Participants were recruited using purposive and "snowball" sampling, yielding 38 semi-structured interviews. Interviews were audio recorded, transcribed and thematically coded. Three key themes were identified - (1) the perceived value of calves; (2) the impact of value on management and welfare; and (3) the importance of simplicity in managing a system at capacity. Overall, replacement heifer calves were perceived as highly valuable and "the future of the herd" while the perceived value of surplus calves was variable. Some farmers prioritized simplicity whereby management protocols were standardized, however others justified suboptimal management practices including feeding poorer colostrum and lower quality milk to surplus calves due to their lower value. Further research is required to assess how these attitudes and behaviors toward calf value influence health and welfare to better inform the development of future calf-focused policies.

The early-life rumen microbiome is highly dynamic, shaped by dietary transitions and maternal influences. Several dietary additives have been studied during the pre- and post-weaning periods to improve animal welfare, growth performance, and farming efficiencies. This study investigated microbial community assembly and growth performance of lambs provided with a mannan-rich fraction (MRF) supplement, either through maternal supplementation, directly, or via a combination of both. Using metagenomic sequencing and gas chromatography, we found differences in rumen microbial alpha and beta diversity related to both sampling time point and MRF supplementation (p < 0.05). At week 8, lamb microbiomes showed greater variance in their Shannon alpha diversity, with direct MRF supplementation only to the lamb resulting in a significantly greater diversity (p < 0.05). At week 20, combined maternal and lamb supplementation resulted in the highest Shannon diversity and was different compared to all other groups (p < 0.05). Beta diversity analyses combined with differential abundance analyses revealed that microbial community structures are driven by both diet and time, with maternal MRF supplementation associated with enrichment of taxa involved in carbohydrate fermentation and succinate metabolism, including Succiniclasticum ruminis, Succinovibrio dextrinosolvens, and Fibrobacter succinogenes. Generalized linear modeling identified significant associations between microbial alpha diversity metrics and total volatile fatty acids in lambs, particularly butyrate and valerate. Furthermore, at week 8, there was a significant positive correlation between alpha diversity metrics and propionate and valerate. In this study, lambs receiving MRF through maternal and direct supplementation had the highest growth performance, measured as the median average daily gains (kg) and final weights (kg) of lambs. These findings suggest that MRF supplementation, especially when provided both maternally and directly, may influence the lamb rumen microbiome and alter its metabolic potential with potential implications for optimizing early-life nutrition strategies in ruminant production systems.

Excessive copper (Cu) supplementation is common on dairy farms worldwide, despite a growing body of research highlighting the risks of over-supplementation, including liver damage, impaired growth, and reduced fertility. However, diagnosing Cu toxicity remains challenging due to the liver’s allostatic regulation of blood Cu levels and debate surrounding toxicity thresholds. This study utilised secondary data from a longitudinal study conducted between September 2016 and September 2018 involving 80 replacement Holstein–Friesian heifers. Data was utilised to generate receiver operating characteristic curves which established liver Cu thresholds associated with suboptimal liver function and fertility. Results indicated that hepatic Cu concentrations exceeding 167 mg/kg of dry matter (DM) were associated with reduced conception rates to first service, while concentrations above 260 mg/kg of DM reduced conception probability to first and second services. Hepatic Cu concentrations exceeding 322 mg/kg of DM were linked to impaired liver function, as evidenced by elevated serum glutamate dehydrogenase activity. In contrast, a toxicity threshold value could not be generated for plasma Cu, underscoring its inadequacy as a biomarker. The fertility thresholds identified in this study may be more closely related to optimizing Cu levels for animal performance rather than indicative of liver Cu toxicity, suggesting the need for further research.

1. This study assessed the impact of feeding a high nutrient specification (HS) diet, recommended for fast growing broilers and a low nutrient specification (LS) diet, recommended for slow growing broilers, on growth performance variables, including feed intake (FI), weight gain (WG) and feed conversion ratio (FCR) and production characteristics of fast growing Ross 308 broilers and slow growing Redbro broilers.2. As hatched, Ross 308 (n = 210) and Redbro broilers (n = 210) were randomly allocated to 28 floor pens, 14 pens for each genotype and fed experimental diets from 0 to 42 d of age over four feeding phases. Each diet was fed to seven pens of each genotype, following a randomised, blocked, factorial design.3. Growth performance variables were determined for each feeding phase. Excreta were collected during the last 4 d of the study to determine dietary N-corrected apparent metabolisable energy (AMEn) and nutrient retention coefficients. At 42 d of age, one bird per pen was humanely killed and samples were obtained for determination of meat quality variables, jejunal histomorphology and liver triglycerides.4. Feeding the HS diet increased FI (p < 0.05), WG (p < 0.001) and reduced FCR (p < 0.001) in both genotypes from 0 to 42 d compared to feeding the LS diet. Feeding the HS diet increased AMEn intake (p < 0.001). Diet did not affect breast meat quality, except for increasing drip loss in Ross 308 broilers (p < 0.05), nor did it affect breast myopathies, jejunal morphology, or liver function. Therefore, feeding the HS diet, which was formulated to meet the nutrient recommendations for Ross 308, can be a practical strategy to improve the feed efficiency of Redbro broilers.

The production of soybean meal (SBM) can be linked to various issues related to the environment (e.g., deforestation, water waste, and transportation costs), and reducing its inclusion in pig diets by using alternative protein sources, such as insect meal, is an important challenge for nutritionists. This study aimed to compare the productive performance, dietary digestible energy (DE), nutrient digestibility, and some blood indices of growing Danube White pigs fed graded levels of Black Soldier fly (Hermetia illucens L.) larvae meal (BSFLM) at 0, 30, 60, 90, and 120 g/kg of diets, in replacement of SBM for 38 days, from 119 to 157 d old. Each diet was fed to eight pigs in individual boxes following randomization. Pigs grew according to breeders’ recommendations and did not have any clinical health problems. Replacing SBM did not change (p > 0.05) the pigs’ growth performance and DE, as only dietary fat digestibility increased in a linear fashion (p < 0.001), possibly due to the high BSFLM, i.e., the high-fat inclusion rate. There was a simultaneous rise in some oxidative damage indicators and an increase in antioxidant status, thus suggesting that further research involving longer feeding periods is needed to identify a potential time sequence of events. Overall, BSFLM is a promising ingredient in pig nutrition.

The effects of exogenous phytase (PHY), xylanase (XYL) and protease (PRO) alone and in a combination, when supplemented to diets based on three field bean cultivar samples with different chemical composition, on dietary metabolisable energy (ME), nutrient digestibility, gastrointestinal tract (GIT) development, feed intake (FI), weigh gain (WG) and feed conversion ratio (FCR) were studied. Diets based on beans with lower phytic acid and fibre content had higher ME, fat (p < 0.05) and dry matter retention (p < 0.001) coefficients, which coupled with greater feed efficiency, e.g. reduced FCR (p < 0.001). Dietary PHY alone reduced FCR (p < 0.001) and XYL alone improved dietary ME (p < 0.05). An interaction (p < 0.05) between enzymes regarding FI and WG occurs, but PHY seems to be the main contributor to improved performance. There was an interaction (p < 0.05) between bean cultivars and enzymes regarding nitrogen retention (NR) as PHY produced a greater coefficient when supplemented with a low phytate diet. The overall weight of the total GIT was not changed by the enzymes or bean cultivars (p > 0.05). The changes observed in different GIT segments are unlikely to have biological significance.

The apparent absorption of copper (Cu) in ruminants is low, with between 0.01 and 0.07 g/g absorbed from sources such as copper oxide (CuO) under typical feeding conditions, resulting in high levels of excretion. Improving the bioavailability of Cu could reduce the supplemental amount required to maintain Cu status and reduce excretion, particularly in the presence of dietary antagonists such as sulfur (S) and molybdenum (Mo). The objective of our study was to determine the Cu status of cows when fed nanoparticle CuO coated with Lys compared with conventional CuO when fed without or in combination with antagonists to Cu absorption (S and Mo) in the diet of dairy cows. Fifty-six multiparous Holstein-Friesian cows that were 48 d ± 17.4 (mean ± SD) post calving and yielding 40.6 ± 6.9 kg milk/d were used in a 2 × 2 factorial design. The 4 treatment groups were; CuO (O-), CuO with added antagonists (O+), nano CuO with a lysine coating (N-), and nano CuO with a Lys coating with added antagonists (N+), fed for 16 wks. We formulated the diets to contain approximately 17 mg Cu/kg dry matter (DM) and diets with antagonists contained an additional 1 g S/kg DM and 6 mg Mo/kg DM, with Lys added to O- and O+ to provide the same daily supply as N- and N+. Blood samples were collected at wk 0, 2, 4, 6, 10 and 16, and liver biopsy samples at wk 0 and 16. We found no effect of dietary treatment on DM intake, milk yield, live weight or body condition score, with mean values of 23.3 kg/d, 40.1 kg/d, 646 kg and 2.68, but milk SCC was higher in cows fed conventional compared with non CuO, or with added antagonist. We also found no effect of treatment on blood activity of gamma glutamyl transferase, superoxide dismutase or ceruloplasmin, hematology profile, or plasma Cu and iron concentration. We found that plasma Mo concentration was increased from 0.36 µmol/L in cows fed O- or N- to 0.80 µmol/L in those receiving O+ or N+. Additional dietary antagonists also decreased the concentration of Cu in the liver of cows fed conventional CuO (C+) over the study period by 1.3 mg/kg DM/d, but in cows fed dietary antagonists and nano CuO coated with Lys (N+), liver Cu concentration was increased by 1.1 mg/kg DM/d. Our study is the first to demonstrate that reducing the particle size of CuO into the nano scale with a lysine coating improves the bioavailability of CuO in the presence of dietary antagonists in dairy cattle, and we did not observe any negative effects on performance or health.

Given the lack of research regarding the effect of microalgal supplementation in dairy cows on milk mineral concentrations, this study investigated the effect of feeding different protein supplements in dairy cow diets on milk, feces, and blood plasma mineral concentrations, associated milk and blood plasma transfer efficiencies, and apparent digestibility. Lactating Finnish Ayrshire cows (n = 8) were allocated at the start of the trial to 4 diets used in a replicated 4 × 4 Latin square design experiment: (1) control diet (CON), (2) a pelleted rapeseed supplement (RSS; 2,550 g/d), (3) a mixture of rapeseed and Spirulina platensis (RSAL; 1,280 g of RSS + 570 g of S. platensis per day), and (4) S. platensis (ALG; 1,130 g of S. platensis per day). In each of the 4 experimental periods, a 2-wk adaptation to the experimental diets was followed by a 7-d sampling and measurement period. Feed samples were composited per measurement period, milk, and feed samples (4 consecutive days; d 17-20), and blood plasma samples (d 21) were composited for each cow period (n = 32). Data were statistically analyzed using a linear mixed effects model with diet, period within square, square and their interaction as fixed factors, and cow within square as a random factor. Cows fed ALG were not significantly different in their milk or blood plasma mineral concentrations compared with CON, although feeding ALG increased fecal concentrations of macrominerals (Ca and Mg) and trace elements (Co, Cu, Fe, I, Mn, and Zn), and reduced their apparent digestibility, compared with CON. When compared with CON and ALG, milk from cows fed RSAL and RSS had lower milk I concentrations (-69.6 and -102.7 μg/kg of milk, respectively), but total plasma I concentrations were not affected significantly. Feeding S. platensis to dairy cows did not affect mineral concentrations in cows' blood or milk, but care should be taken when rapeseed is fed to avoid reducing milk I concentrations which may in turn reduce consumers' I intake from milk and dairy products.